Introduction

Though I've owned and reviewed many different tonearms in the past they have all been pivoted - unipivots, gimballed bearings, weird designs like the Dynavector 507 etc, but not one parallel tracker, partly because I couldn't really see the point. But despite (perhaps because of) this prejudice I jumped at the chance of reviewing Len Gregory's "Conductor" air bearing arm - now to see what all the hype was about...

Theory

The basic premise of a parallel tracker is childishly simple. When a record master is cut, the cutting head tracks across the disk in a straight line from the edge to the centre of the record. When replayed by a pivoted arm the cartridge/stylus swings in an arc; radius the effective length of the arm. Thus even if perfectly set up, the stylus will only have correct lateral alignment (or Zenith) on two points of the disc - the so-called "nulls". Everywhere else there will be some angular error up to just over 2 degrees(*1). Tiny errors in either cartridge angle in the headshell, or overhang can have major effects on the position of the nulls - for example a 2 degree error in Zenith can move both nulls right off the record!(*2)

Enter the parallel tracker... Here the cartridge is held on an arm which doesn't rotate around a point, but rather runs along some track so that the stylus describes a perfect straight line just like the cutting head, with zero misalignment. This sort of thing has spawned various families of sled, ones which are powered across the disc by a motor, others on little bearing wheels and perhaps the most famous the air-bearing arm.

In an air-bearing, the armtube is usually supported on a tube (lets call it the carriage) which is wrapped round another tube which has holes in it which air is pumped through (let's call it the air-beam). The arm carriage is a close fit to this drilled air-beam and so a cushion of air is formed between the two such that the carriage does not actually touch the air-beam. There are many variations on this theme but the basic principle is the same. The result is a bearing with as near zero friction as is possible. However even air-bearing arms divide roughly into two groups.

The first are high-pressure, typified by the Eminent-Technology and Kuzma arms. In these the air gap is very, very small and the resultant air cushion only a few molecules thick. This requires very high precision and a high-pressure pump to maintain that wafer thin layer of air. The advantages claimed are that this makes the bearing not only zero friction, but very rigid in the twisting plane.

The second are low-pressure bearings, originally pioneered by the no-longer-made Forsell and now the Conductor. These things are obviously relative but for this type the air-gap is much thicker and more cushion-like. The required pump produces less pressure but greater volume of air, as air is lost to the bearing at a much higher rate. This cushion will also have the effect of isolating the cartridge/armtube and carriage from the rest of the arm and turntable. Resistance to twisting will be partly dependent on the wide carriage being supported for some length along the air-beam and also the inertia of the structure itself.

Now I'm probably pushing an analogy here but it seems to me that the relationship between the "high-pressure" and "low-pressure" philosophy has some parallels with the gimballed vs unipivot debate. The former being theoretically much more rigid in the twisting plane, the latter relying on inertia to prevent twisting at audio frequencies and offering some isolation for the arm.

Construction (and more theory)

Which brings us to the arm under review here - The Conductor.

I'm a great fan of the KISS (Keep It Simple Stupid) philosophy of arm construction and I was surprised at how incredibly simple the arm is. The parts count is vanishingly small and all is assembled to produce a not unattractive arm with a rather "engineered" finish rather than camera chrome etc. The arm mounting and support is all machined aluminium and a simple and effective arm lift is provided.

The air-beam is made from chrome-plated brass and the carriage tube from aluminium. This is important because the chrome air-beam has a mirror finish and being chrome is much harder than the aluminium carriage. That means that even if mishandled the carriage cannot scratch the surface of the air tube. Likewise most dust particles will not be able to mark it and it's easy to clean.

The construction of the air-beam is interesting and unique in that air is supplied via two clear plastic tubes to either end of the structure, and the air-beam itself has an internal division half way along it's length. This is designed to keep the air pressure as constant as possible right across the tube. Along the top of the tube run a series of tapered holes where the air exits to support the carriage. Obviously at any one time only a few of these holes will be covered by the carriage tube and so much air escapes uselessly, one reason for a high capacity pump.

The armtube is a thin carbon-fibre tube looking too weedy for the job. However carbon fibre is several times stiffer for a given mass than any metal so appearances can be deceptive. It looks like the fibres are aligned along the arm rather than being woven, this maximising resistance to bending at the cost of less resistance to twisting, you see the same sort of tube in expensive kites and badminton rackets. The headshell is a machined aluminium structure glued to the armtube the connection between armtube and carriage is by two cross-head bolts that allow azimuth adjustment and changes in arm length during setup. Counterweight is a simple black painted affair (brass?) held in place by O-rings.

Air is supplied by a fish-tank pump - this has a variable output, and an air tank (plenum chamber) is placed between the pump and arm to smooth flow. The arm is available as a kit without these two items and it would be very easy to make your own tank (as I did) with a plastic bottle and a glue gun.

Set-up and Adjustment

I approached this with some trepidation having never used such an arm before. But I needn't have worried; though initial set-up is more complicated than on most pivoted arm, getting it spot-on was easier.

First thing to set up is arm height. It's a simple allen-bolt then wiggle affair, and as all other alignment settings are lost the minute you touch it, it has to be done first. Here I just set the armtube horizontal (more on this later...). Then you need to set the alignment by placing a gauge with a straight line drawn on it from the centre spindle to the edge of the platter. By altering the angle of the air-beam and the length of the armtube it's very simple to do this so that the stylus is on the line right across the record. Once done this alignment is perfect, any error very easy to spot. A pivoted arm needs precise overhang adjustment to get the equivalent, is difficult to judge and as I mentioned before even tiny errors can have a major effect on the position of the nulls(*3) none of that malarkey here...

An aside - Here I'll add that most two-point gauges are clumsily produced (as Werner has found) with poor printing, spindle holes off centre. Gauges with one point and a line-of-sight method where sighting along a line to the point of an arms pivot are equally inaccurate, as most arms don't have this point marked in any way.

Then (and sort of at the same time) the air-beam must be levelled using four tiny grub-screws, this works very well and is ESSENTIAL as the tiniest deviation will make the arm difficult to use, as when cueing the arm will drift one way or another until it finds a groove, let alone the effect on stylus/record wear and sound quality. This is a good indication of how frictionless that bearing is - if you get it wrong it's painfully obvious.

Last off is fine adjustment of the angle of the cartridge in the headshell. By twisting the cartridge in the headshell you can get the cartridge cantilever to align 90 degrees to the line from centre to edge of the record. The cartridge is now perfectly aligned at all points of the record, though if the stylus is poorly aligned in the cantilever you might have to do fine adjustment by ear with further twisting of the cartridge in the headshell.

It all sounds complicated but in fact I found it much easier than any pivoted arm to get spot-on as errors were so easy to spot.

Now to the thorny subject of VTA and VTF...

The Conductor is weird... it has a very high centre of gravity. If you lift the arm at the headshell after about 40 mm the downforce will be zero and the arm will try to flip over on its back - stopped by a small rubber ring fitted for the purpose. This is very odd behaviour. It means that when you raise the back of the arm to increase the VTA, at the same time the VTF (Vertical Tracking Force) will increase, loading the cartridge cantilever and thus reducing the VTA - and visa versa. Couple this with the difficulty with changing VTA (i.e. all other settings are lost) and you can see that for those who believe critical VTA a vital part of arm set-up and something which needs changing for every record the Conductor is an absolute non-starter.

Happily I like to set and forget such things so I slid the weight to give recommended VTF and set the arm horizontal - and then pondered the possible positive effect of this strange behaviour. When a cartridge rides a warp the VTF will reduce fractionally on the way up, the opposite of most unipivots and generally a good thing - indeed Roksan have a clever swinging counterweight to try and achieve the same effect. How significant this actually is, is open to debate but this coupled with the very low vertical effective mass makes the Conductor superb over warps.

Ah! Mass...

Air-bearing arms all share one characteristic, a very flat 'ellipsoid of inertia', i.e. the effective mass in the vertical plane is much lower than that in the horizontal plane. If you think of a see-saw, moving it up and down is pretty easy compared to dragging the whole thing across the ground:-)

The zero friction bearing helps, but the cartridge will still see the entire mass of the carriage, armtube, cartridge and counterweight which it has to accelerate in order to move it. On the other hand in the vertical plane the arm acts as a normal pivoted arm in that the cartridge sees only the inertia of the armtube as it is balanced. The shorter armtube of a parallel tracker further reduces this. Calculating effective mass of an arm requires a lot of complex math and detailed knowledge of the disposition of the masses in the arm so I can't do it here. But if a typical medium-mass arm (e.g. Rega 300) has an effective mass of say 12 grams, the Conductor will have something like 5 grams in the vertical plane and 30 horizontal (these are pure guesswork as an example, not actual figures!).

What does this mean in practice? Using the Music Maker III cartridge (high/medium compliance) the vertical resonance of the arm/cartridge is around 15 Hz, in the horizontal plane around 5 Hz. Either of these figures in a pivoted arm would be cause for concern as the former is very near the audible band (so very low bass notes would cause this resonance) and a lighter and/or more compliant cartridge might push this figure up to 20+ Hz where you'd be in big trouble. The latter figure of 5Hz is very near warp frequency meaning a pivoted arm would bounce all over the place on the tiniest warp - Bad!

But warps are in the vertical plane where resonance is a safe 15 Hz and low bass notes are recorded just in the horizontal plane (in effect they are mono) where resonance is a safe 5 Hz - if these things weren't the case then all parallel trackers would be history:-)

The arm can be supplied with any one of three counterweights and I had the medium one. I'd recommend trying the lightest you can get away with, certainly in my case there was loads of counterweight stub to play with and a weight half as heavy would have had the dual advantages of reducing considerably the overall mass of the carriage/arm assembly and thus horizontal effective mass, whilst at the same time increasing the vertical effective mass slightly.

In Use

Not a huge amount to report really - once set up it was very easy to use, cueing being no more difficult than most conventional arms and easier than some. The only exception being with those very thin records with a significant edge bulge - with these sometimes the stylus would run down the 'slope' of the bulge for a couple of grooves before catching. This is a result of that high horizontal effective-mass, and a lighter counterweight could well have tipped the balance - you get the same problem with very compliant cartridges on heavy arms. But it was rare.

The other moan was noise. Not surface noise (more on this later) but the sound of the pump was like distant road repairs and the arm itself 'hissed' like a cobra. The former was solved by drilling a hole in the living room wall and installing the pump in the understairs cupboard - the things I do for TNT! If that solution isn't practical it should be possible to find a quieter (medical?) pump. The hissing you just have to live with, it's the nature of the beast. If your turntable is right next to the listening position it might be a problem, otherwise forget it.

Playing with the pump was interesting. Without the reservoir tank the arm picked up a kind of hum from the pump (air pulses?), the tank stopped it completely. Also with a variable output it seemed that the best performance was with the lowest practical setting, i.e. enough air to support the carriage but not more. Why that was I'm not sure. The hissing was less obviously and perhaps the "softness" of the air cushion had an effect - who knows?

Lastly dust... I live in a very dusty house, wood fires, carpets and old furniture complete with kids to bounce on it. I thought any air-bearing arm would be in deep trouble with this but no, the conductor was fine. After a day unused, some dust would build up but just switching on the pump and moving the carriage up and down the air-beam blasted any dust off, in three months it's never stuck. Whether a high-pressure arm would be so forgiving I don't know.

Sound

"At last!" I hear you cry...

Naturally enough, for this first test I used Mr Gregory's own Music Maker III cartridge. I was also supplied with a rather special turntable from Acoustic Solid which proved a perfect visual and sonic match.

Generally speaking after setting up a new arm/turntable or cartridge my first port of call is Simply Red's "Sad old Red". It's the second track on their album "Picture Book" - and it goes on first because it has a lovely walking bass line that picks out bass resonance anywhere in the system - you'd be amazed at how many components stumble over this simple test. One high-end manufacturer brought prototypes of his latest 5000 euro speakers and left knowing they needed work after this test...

But I digress. The thing is that sometimes I drop the needle right on that track, and sometimes I'm lazy and just drop it on the start of the side and fart about getting comfy whilst waiting for the main event.

This time I was lazy...

Except I didn't fart about, I was stopped in my tracks by what was coming out of the speakers - suddenly there was a lightening fast (and I don't mean playing) and tuneful bassline, a track that normally I'd put as average was grabbing my attention. When "Sad old Red" came on the bass line was beautifully handled, the fact that the player used his fingers rather than a plectrum obvious, the whole thing beautifully held together. The drumkit back in the mix perfectly produced. The arm/cartridge combination was a real detail miner as well, it was one of those times when new details kept popping up, but it didn't sound unnatural or forced - just "correct".

So of course the LP stayed on - at track 4 which on my worn copy sometimes sounds a little squashed and edgy the fidelity didn't change - in fact I could have been listening to a CD (did I really say that?). This new discovery sent me digging through old favourites to see if that right-across-the-record ability would revitalise my collection - Led Zep 4, Live and Dangerous, Beggars Banquet etc all were spun that evening with increasing glee. I know that here we're not talking about audiophile disks, but all showed problems with other arms that the Conductor sailed through - it was an addictive experience. My own Dynavector 507 does this trick but only on the best records - the others I've learnt to accept as flawed - no longer.

At the same time the realisation came across that I was hearing perhaps the most detailed and controlled performance ever from these records and for that alone the arm was winning me over. On the down side the combination lacked the ultimate heft and "slam" (what a horrid word) of something like an Ekos or even SME4, but it was good enough in these areas that I didn't feel too robbed.

There is a caveat here - the Conductor did expose poorly pressed or recorded material. It didn't do the trick of opening up compressed performance or adding warmth and bass where there was none. A classic example was 'Best of Bruce Springstein' which o the Conductor sounded flat, hard and the REL Strata (set to roll-in under 60 Hz) hardly bothered. Ultimately if you want your arm to act as a subtle effects box look elsewhere - here you get what's on the disc...

Moving on to really atmospheric audiophile recordings like the Sheffield Labs direct cut of "King James", showed once again huge levels of detail and fine soundstaging but a slight lessening of dynamic contrasts compared with the best - in this more reminiscent of the Triplanar than the SME4 on my Orbe - perhaps partly down to the different turntable.

Surface noise was something of a revelation. I thought I'd killed this as best I could with the lovely Dynavector 507, but the Music Maker was even better and in a rather interesting way. What crackles there were, seemed to come from beyond the speakers, to either side of the musical main event between them - it sounds odd but it means that by being physically separated from the music it becomes much less of an irritation. (*4)

The soundstaging was superb, I'd heard tales of airbearing arms having wandering images but everything seemed rock solid and open here, depth being particularly good.

Then I put on the Dynavector XX-2 to see how the arm would handle a very different kind of cartridge. Boy what a chameleon! The presentation was hugely different - warm and easy and laid back, a gentle flow where the Music Maker was digging for detail. The bass softer and rounded but still tuneful and on-the-button. Never had an arm shown the differences between these two cartridges so graphically, in fact in one respect it makes this review rather limited because I suspect that with another cartridge the presentation would be different again. As always the question arises as to whether the arm was wonderful because it allowed the character of each cartridge to come to the fore, or flawed because it couldn't cope with such changes, but as in both cases the performance was excellent I strongly suspect the former. I know I've said similar things in my Dynavector 507 review, but here the effect was even more marked.

Returning to the subject of surface noise - the XX-2 + Conductor just ignored it - even my most abused 'student days' records seemed to come through with only the faintest crackle. In an age of second-hand vinyl this ability cannot be overstated.

One problem for any reviewer doing this job long term is that you become jaded, and also fed up of ripping your 'perfect' system apart to listen to some new piece of kit. Often I'll listen to something knowing that it is "work" rather than pleasure and get the whole thing over and done with as quickly as possible. In this case I've had the arm in my system for three months and delayed and delayed the review so I could try more records, different settings and cartridges and most importantly, so I could enjoy it as long as possible! In that time other reviews have been shelved because I didn't want this one disrupted by amp/speaker changes and I certainly didn't want to listen to CDs!

So I suppose it's time to try and pin down what makes this such a special arm. Giving an overall 'character' is difficult as it seems to be so cartridge dependent - something that means that whatever the balance of your system or tastes you should be able to get the sound you want. In fact it's easier to list its faults:-) The noise of pump and "hiss" I've already mentioned. It's also not as expansive or hugely dynamic as the best of the big gimballed arm brigade. With that Henry James recording the hall is bigger with the Dynavector 507, the snare drum strikes that bit harder on the SME and so on.

But to call these faults is pushing a bit, the same could be said of the Morsiani, the Triplanar or the Audiomeca Romeo, it's just a different presentation. Certainly the Conductor is much closer in these areas when partnered by the Music Maker III than with the XX-2. However if you love the flow and ease of the Triplanar then again the Conductor can get close if coupled with the XX-2. I guess the conclusion would be that the Conductor shows little character.

As for that ability to get detail off the disc, it's not generally something I put as number one on my list of priorities, but the Conductor seems to place such extra detail perfectly in the context of the music, not a rabbit-out-of-a-hat effect where that extra detail grabs your attention away from what is going on. The latter is often the result of an arm picking one frequency and pushing it, and the information it contains further forward in the mix - it's artificial and you generally lose as much as you gain. The Communicator just seems to be able to separate every strand of the music, extract the information contained, and then reconstruct the original event. It all hangs together beautifully. It also means some records that previously I'd considered fillers made sense and became interesting.

But given that other arms match it in some areas, better it in others why did I hang on to it like a drowning man? Because it is the least irritating arm I've ever used... I could listen to the tubular bells at the end of "Tubular Bells" without wincing despite my having played it a thousand times. Records, and here perhaps a 1/3 of my collection, that were worn or just noisy became listenable and showed true fidelity. Records in good condition showed new insight and detail to the extent that I was happy to live with the 'weaknesses'.

So now the Conductor comes out of the system and I will play for hours - days perhaps to get the alignment spot on with my other arms. Maybe I'll be able to reproduce that beginning-to-end fidelity of the Conductor, but it'll not be easy - with the Conductor such considerations just don't seem to matter.

The 'Solid Machine' that partnered the Conductor just got on with the job,
it's the sort of turntables dealers love - bomb proof, simple, a doddle to
set up and looking a million dollars. Performance was certainly good enough
to show the Conductor's capabilities and I was impressed enough to ask to
keep it for an extended period so it could be included in my series of
turntable tests - watch this space...

Conclusion

Over the last 20 years I've been lucky enough to have used a wide range of state-of-the-art pivoted tonearms. Obviously I haven't heard every arm manufactured, but those I have cover almost all the various pivoted solutions to the problem of extracting music from vinyl. During this period I've rather dismissed air-bearing arms as being complex, fussy and expensive solutions to a problem that doesn't really exist. The Conductor has changed all that. In certain fundamental ways, most notably it's fidelity across the disc, it is superior to any pivoted tonearm I've been fortunate enough to use. That the Conductor is simple, reliable, easy to use and cheaper than most of the aforementioned arms is only the icing on the cake. Is it the best arm I've ever heard? - forgive me if I vacillate at this point, there are so many good arms out there, and some have really impressed me in certain areas. But as with the Girl-With-The-Curl it is a case of "when they are good they are very, very good" - the Conductor was good all the time. So lets ask the question in a different way - Is this the arm I would take to my desert island? Given my taste in music, my sub-optimal record collection? Yes, especially if I could take a box full of cartridges:-)

(*1) Interesting that in a world where people claim that errors of VTA of less than 0.01 degrees are audible and significant, the same writers seem happy with lateral errors of over 2 degrees (my Dynavector 507 is 2.2 degrees out at edge-of-disc), the two things are obviously not directly comparable but it's interesting nevertheless...

(*2) For example a 1 mm error in overhang (hardly visible and many gauges aren't that accurate) will move the position of the two nulls by about 10mm on a 9 inch arm with longer arms being worse. Misalignment of the cartridge in the headshell (thus changing the offset angle) is just as bad - a 0.4 degree error producing a 5mm movement of nulls. ("Tonearm Geometry and Setup" by Martin D. Kessler and B.V.Pisha, published in "Audio" Jan 1980)

(*3) An aside - The alignment of cartridges generally depends on large printed gauges of one kind of another - even those supplied with arms are generally woefully inadequate (as Werner has found) with poor, inaccurate printing, spindle holes off centre etc. Gauges with one alignment point using a line-of-sight method where you sight along the line to the point of an arms pivot are equally inaccurate as most arms don't have this point marked in any way. When working to such small errors this sort of thing makes the getting of proper alignment on a pivoted arm very much hit and miss. The metal overhang/alignment gauge supplied with the Dynavector 507 being a notable exception but one that requires a removable headshell.

(*4) I emailed Mr Gregory about his effect on surface noise and he replied with the following which I reproduce here as it is worthy of consideration.

"My theory about the clicks and pops and surface noise being thrown outside the audio image; I would move to say that this proves that the musical information which is 'in phase' is actually being more accurately projected 'in phase' by the cartridge and Conductor whereas the 'out of phase' damage and noise detritus which is certainly not 'in phase' gets thrown out of the 'in phase' audio image, which is where it should be as 'out of phase' information - I doubt whether a pivoted arm could achieve this particular effect. Think of the forces involved in just maintaining a pivoted arms consistency of travel and minimising its geometric anomalies - I think we are looking a micro information which is beyond pivoted arm technology"